Admin orders custom sortable column in WooCommerce with HPOS

I recently upgraded a Woocommerce website to use HPOS and I found out the custom column sorting no longer works. In Woocommerce I setup a sortable column for a customers last name. I adjusted my code to use meta_query to sort orders based on _shipping_last_name but no results are returned. I have a column that shows the correct last name value, but the sort feature doesn't sort.

Here is the sorting code currently:

function hpos_args( $query_vars ) {

    if(isset($query_vars['orderby']) && $query_vars['orderby'] == 'customer_user'){
        $query_vars['meta_query'] = array(array(    'key' => '_shipping_last_name' ));
        $query_vars['orderby'] = array('meta_value' => $query_vars['order']);
    }

    return $query_vars;
}
add_filter( 'woocommerce_order_query_args', 'hpos_args', 10, 1 );

'customer_user' is the column title, the values in the column are the meta_value for _shipping_last_name

When you have only one meta key, simply use "meta_key" query argument instead.

Also, you need to target "customer_user" order_by query string argument like:

// Define custom sortable column(s)
add_filter( "woocommerce_shop_order_list_table_sortable_columns", 'custom_admin_order_list_sortable_columns' );
function custom_admin_order_list_sortable_columns( $sortable_columns ) {
    $sortable_columns['customer_user'] = 'customer_user';

    return $customer_user;
}

// Alter the query for custom sortable column(s)
add_filter( 'woocommerce_order_query_args', 'filter_admin_hpos_order_lists', 10, 1 );
function filter_admin_hpos_order_lists( $query_args ) {
    if ( isset($_GET['orderby']) && $_GET['orderby'] === 'customer_user' ) {
        $query_args['meta_key'] = '_sorting_name';
        $query_args['orderby'] = array('meta_value' => $query_args['order']);
    }
    return $query_args;
}

Code goes in functions.php file of your child theme (or in a plugin). Tested and works.